This application claims the benefit of German Patent Application 100 63 362.5, filed Dec. 19, 2000, which is relied upon and incorporated by reference herein.
1. Field of the Invention
The invention relates to a brake pad, in particular used for disc brakes, comprising a metal back plate provided with profiles and at least one friction lining attached thereto.
2. Background of the Invention
A brake pad is disclosed in the DE-A 197 06 123, in which the back plate has at least two sections with different thickness in circumferential direction. The sections at the same time should be designed to relieve the thermal stress on an activation element that operatively engages the brake pad. Described are wave-shaped profiles, rectangular profiles, indentations, depressions or the like. Even if a certain thermal de-stressing or uncoupling can already be realized with this, undesirable temperatures resulting from increased braking forces are still effective in the region of the activation element, particularly the brake cylinder or its peripheral components, which can result in damages.
A brake pad having a metal back plate with a friction lining (e.g. the brake pad) attached to it is also disclosed in the U.S. Pat. No. 6,041,893. The area between friction lining and back plate contains at least one additional layer, to which certain damping qualities are assigned and which sounds acoustical warnings when the friction lining is abraded.
It is the object of the invention to optimize a brake shoe, so as to avoid any temperature-dependent damage to the activation element, especially to the brake cylinder or the peripheral components cooperating with it.
This object is solved with a material having lower heat conductivity, relative to the friction lining, at least in some profile sections. Advantageous modifications of the subject matter of the invention follow.
According to a modification of the prior art, in particular the DE-A 197 06 123, the subject matter of the invention permits a clear uncoupling (e.g., dissipation) of the heat flow between friction lining (e.g., of the brake pad) and activation or actuating element, especially the brake cylinder, as well as all components connected thereto, such as sealing members or the like. The frictional heat transferred in particular from the brake disc to the friction lining when the brake cylinder(s) is (are) activated thus no longer disseminates directly to the metal back plate and therefore also the activation element. Rather, the subsequently installed material with low heat conductivity, provided in particular in the profiles, mostly compensates for the temperature.
A further uncoupling (dissipation of heat) of the temperature flow is realized with the special profile design, particularly the raised areas that extend only partially in the direction of the activation element. The segment-like raised areas, in particular arranged partially along the periphery of a circle, essentially remain inside the diameter (the cross-sectional surface) of the activation element(s), so that the area of contact between said element(s) and the metal back plate is limited to these segments.
According to another inventive idea, the material with lower heat conductivity can either be provided only in the region of the profiles or can be arranged such that it extends over the imagined circular periphery of the segments. Alternatively, the material with low heat conductivity can also be allowed to extend essentially over the cross-sectional surface of the friction lining, between the lining and the metal back plate.
The metal back plate can either be a cast iron plate with formed-in profiles or a conventional steel back plate with corresponding embossed areas. The profiles projecting from the metal back plate in the direction of the activation element preferably have a height of  less than 2 mm, in particular of between 0.5 and 1.0 mm.
The raised areas resulting from the profiling of the metal back plate have the following advantages:
a reduction in the heat conductivity;
a reduction in the heat radiation;
an increase in the convective heat transfer to the environment.
The subject matter of the invention preferably is used with all disc brakes (hydraulic and pneumatic). This solution also makes it possible to dispense with additional layers, as described in the prior art according to the U.S. Pat. No. 6,041,893.
Preferred materials for the profiles, which exhibit decreased thermal conductivity compared to the frictional lining comprise, consist essentially of and consist of as well as their compounds, the following components: magnesium oxide, vermiculite, fibers, in particular PAN (polyacrylnitrile) fibers, rock wool, recycled materials and resins, especially phenol resins; also conceivable are admixtures of silicic acid and glass fibers as well as wollastonite. The following is a list of possible ranges for materials with low heat conductivity (all information provided in weight %):
The subject matter of the invention is shown in the drawing with the aid of an exemplary embodiment and is described as follows.